Fish Health Management Lesson 1 PDF

FISH HEALTH MANAGEMENT DR. JOHN MICHAEL T. FIGURA DVM, MSc, DIP.PCCP, PSVSCA  What is Fish Health Management? ✔ Fish health management is a term used in aquaculture to describe management practices which are designed to prevent fish disease. ✔ Once fish get sick it can be diffic...

FISH HEALTH MANAGEMENT DR. JOHN MICHAEL T. FIGURA DVM, MSc, DIP.PCCP, PSVSCA  What is Fish Health Management? ✔ Fish health management is a term used in aquaculture to describe management practices which are designed to prevent fish disease. ✔ Once fish get sick it can be difficult to salvage them. ✔ Successful fish health management begins with prevention of disease rather than treatment. ✔ Prevention of fish disease is accomplished through good water quality management, nutrition, and sanitation.  What is Fish Health Management? ✔ The fish is constantly bathed in potential pathogens, including bacteria, fungi, and parasites. ✔ Daily observation of fish behavior and feeding activity allows early detection of problems when they do occur so that a diagnosis can be made before the majority of the population becomes sick. ✔ If treatment is indicated, it will be most successful if it is implemented early in the course of the disease while the fish are still in good shape. The Significance of Fish Disease Fish disease is a substantial source of monetary loss to aquaculturists. Production costs are increased by fish disease outbreaks because of the investment lost in dead fish, cost of treatment, and decreased growth during convalescence. Usually other circumstances must be present for active disease to develop in a population. Management practices directed at limiting stress are likely to be most effective in preventing disease outbreaks. Relationship of Environment between Fish and Pathogens: Presence of the fish pathogens will result in epizootics only if unfavorable environmental conditions exist and the host defense mechanism has been compromised. If the If it is marginally If it is relationship is changed, a unsatisfactory, balanced, good chronic disease poor growth and health and problems and overt disease will growth will reduced growth result occur will occur. Factors affecting on the Fish Health: Some of the notable symptoms of healthy fish: The shape of the head of a healthy fish never seems bigger than the body. The body and the scales will be very bright. The gills are red in color and will have no spots or sores. Shining Fins & Natural Tail Color are intact No Takes Wounds Feed on the in Time Body Never Seen Never come on the to the Edges surface of the pond of the Pond  Fins and Tail Loss of Wounds Eyes Enlarged Necrotic Natural Color on the Body and Exophthalmic Loss of Breaths Stability & with Mouth Homeostasis Gills loose natural Distended Red color –Pale in Abdomen – Colon Color or Necrotic filled with Fluid Fish Comes to Heavy Mucous Surface & Swims Loss of on the slowly very often Edging Appetite Body & Gills The tendency of fish diseases is more or less depending on the season. We can divide the diseases of fish into the following few parts – Fungal Disease Bacterial Disease Parasitic Disease EUS Nutritional Deficiency Problems Environmental Related Problems Protozoan Parasites Helminth Parasite Crustacean Parasite At present fish farmers are facing all kinds of fish diseases. In general, I will discuss all those fish diseases here. Introduction to Aquaculture Aquaculture: The farming of aquatic organisms, including fish, crustaceans, mollusks, and plants. Goal: Meet the rising demand for food fish as the human population grows. Global Growth and Regional Focus Aquaculture has seen significant growth, particularly in Asia, due to increased yields from fish farms. Phases of Aquaculture 1. Hatchery Phase Purpose: Raise young organisms in controlled environments to ensure high survival rates. Use of Tanks: Hatcheries commonly use tanks to protect and monitor young fish. 2. Nursery Phase Transition phase where young organisms are further nurtured before moving to larger systems. Containment Options: Ponds, tanks, and floating cages. 3. Grow-out Phase Final phase where organisms reach market size. Harvesting: Fish are harvested when they reach the desired weight or maturity. Aquaculture Production Systems 1. Extensive System Low stocking density. Lower input costs; often reliant on natural resources (e.g., natural food and water). 2. Semi-Intensive System Moderate stocking density. Requires some supplemental feeding and moderate levels of input. 3. Intensive System High stocking density. High resource input (feed, oxygen, etc.), leading to higher risks of stress and disease. Ideal for maximizing yields but has challenges related to environmental stressors and disease outbreaks. Disease in Aquaculture Disease: Abnormality in structure or function of aquatic organisms, displayed through symptoms. Symptoms: May include lethargy, visible lesions, erratic swimming, and reduced feeding. Disease in Aquaculture Causes of Disease Infectious Agents: Viruses, bacteria, fungi, and parasites. Poor Management Practices: Overcrowding, inadequate water quality, and substandard feeding. Environmental Factors: Poor water quality, temperature fluctuations, and pollution. Indicators of Disease Tissue or organ damage. Slower growth rates and reduced size. Increased mortality rates. Consequences of Disease Production losses, decreased product quality, and potential rejection in markets. Persistent disease outbreaks can lead to the collapse of aquaculture facilities and threaten industry sustainability. Disease Management and Mitigation Strategies Preventative Approaches Good Management Practices: Proper stocking densities, high water quality, and balanced diets. Biosecurity Measures: Preventing disease introduction through quarantine and disinfection protocols. Therapeutic Interventions Use of vaccines and antibiotics (under strict regulation) to treat specific diseases. Research in novel treatments such as probiotics and immune boosters to enhance resistance in farmed fish. Disease Management and Mitigation Strategies Innovative and Sustainable Methods Integrated Multi-Trophic Aquaculture (IMTA): Combines different species to balance nutrient cycles and improve ecosystem health. Recirculating Aquaculture Systems (RAS): Recycles water to reduce waste and minimize environmental impact. HOW DISEASE DEVELOPS Disease development in aquaculture systems involves three main factors: Host: The farmed fish or aquatic animal. Pathogens: Disease-causing organisms such as bacteria, viruses, fungi, or parasites. Environment: The surroundings and conditions in which the fish are raised. Hosts A host can either resist or be susceptible to a particular disease. Resistance or susceptibility depends on several factors: Age or Size of the Host: Younger or smaller organisms may be more vulnerable. Species of the Host: Some species have natural resistance to certain diseases. Defense Mechanisms: Includes both innate and adaptive immune responses. Health and Nutritional State: Healthy, well-nourished fish are generally more resistant to disease. Pathogens Classification of Disease Agents (Pathogens) in Aquaculture 1. Physical Agents Examples: Extreme temperature changes, ultraviolet radiation from the sun. 2. Chemical Agents Cause disease through environmental contaminants, toxins, nutritional imbalances, and overdoses of drugs or chemicals. 3. Biological Agents (Infectious Disease Agents) Types: Viruses, bacteria, fungi, and parasites. Often found in water or sediment as part of the normal flora. Environmental factors such as temperature, dissolved gases, pH, and food availability influence their presence and numbers. Characteristics of Infectious Agents Direct Transmission: Ability to infect hosts directly. Multiplication in Host Tissue: Capacity to grow and reproduce within the host. Transmission Modes of Infectious Agents 1. Vertical Transmission Pathogens are transferred from parent to offspring. Disease can be passed through the egg or sperm if the broodstock are carriers. 2. Horizontal Transmission Pathogens spread to hosts via water, feed, or carrier animals in the environment. Environment Components of the Fish Culture Environment Water and Holding Systems: Includes tanks, ponds, cages, pens, and other containment systems. Importance of Environmental Stability Health of cultured fish depends on the stability of physico-chemical parameters in the water. Factors that can affect stability: Fish culture activities. Natural causes and fluctuations in the water environment. Environment Key Water Parameters Influencing Fish Health Temperature pH Salinity Dissolved Oxygen Deviations from the optimal range for these parameters can cause stress, which may lead to disease. Environment Successful Fish Culture Requires understanding and managing the fish’s environment. Environmental Role in Disease Prevention and Control: Recognizing how environmental factors impact disease helps in effective prevention and control of disease in cultured fish. Human Factor Importance of the Human Element in Aquaculture Success in aquaculture depends significantly on knowledgeable and skilled personnel. Aquaculture technicians and staff should have a deep understanding of the species they are culturing. Human Factor Consequences of Inadequate Experience or Staffing Insufficient knowledge or personnel can result in costly mistakes. Lack of experience may lead to reduced yields and inefficiencies in production. Human Factor Role of Farming Strategies Effective farming strategies should prioritize the essential role of personnel in each production stage. Ensuring proper training and adequate staffing is vital for achieving high productivity and successful aquaculture operations. Stress in Disease Development Stress Factors in Cultured Fish Common stressors include: Handling Overcrowding Malnutrition Poor environmental conditions Definition of Stress Stress is the sum of physiological responses that fish make to maintain or regain normal balance. Phases of Stress Response (Adapted from Roberts 1978) A. Alarm Stage The fish attempts to escape from the stressor or problem. B. Adaptive Stage If escape is not possible, the fish’s body reacts to the environmental change. The fish tries to adjust physiologically and behaviorally to reach a new equilibrium for survival. Phases of Stress Response (Adapted from Roberts 1978) Consequences:While adaptation may occur, growth, reproductive capacity, and disease immunity may decline compared to previous levels. This stage is when disease problems are most likely to occur. Extended exposure to environmental deterioration can disrupt normal functions and decrease survival chances. Phases of Stress Response (Adapted from Roberts 1978) c. Exhaustion Stage If the environmental change is too extreme for adaptation, the stress response reaches exhaustion. This stage may ultimately lead to the death of the fish. Impact of Environmental Changes Abrupt changes in salinity, pH, or temperature, particularly beyond tolerable ranges, significantly stress fish. Increased stress makes fish more susceptible to secondary infections from opportunistic microorganisms. Stress can weaken the fish’s defense mechanisms, further compromising health. DISEASE DIAGNOSIS Overview of Disease Diagnosis in Fish Involves recognizing abnormalities and identifying their causes. Diagnosis of fish diseases is a relatively recent service in aquaculture. Challenges in Fish Disease Diagnosis The range of laboratory procedures available for diagnosis is still limited. Findings are often not definitive; however, eliminating certain possibilities can still be helpful. DISEASE DIAGNOSIS Importance of Close Supervision A meaningful diagnosis is more likely when fish are under close supervision. Fish farmers should provide detailed information on: Environmental Parameters: Water quality, temperature, salinity, pH, etc. Management Practices: Feeding routines, stocking densities, and handling procedures. Collaboration for Effective Diagnosis Effective communication between fish farmers and diagnostic laboratories enhances the quality of diagnosis and treatment strategies. Signs of Diseases Importance of Close Supervision A meaningful diagnosis is more likely when fish are under close supervision. Fish farmers should provide detailed information on: Environmental Parameters: Water quality, temperature, salinity, pH, etc. Management Practices: Feeding routines, stocking densities, and handling procedures. Collaboration for Effective Diagnosis Effective communication between fish farmers and diagnostic laboratories enhances the quality of diagnosis and treatment strategies. Signs of Diseases Early Signs of Disease in Fish Sick fish often show signs of illness before succumbing to disease. Initial Indications: Reduced Feeding: One of the first signs of illness. Behavioral Changes: Abnormal changes in color and behavior are among the earliest signs. Fish may exhibit the following behaviors: Isolation: Staying away from the school. Surface Swimming: Swimming near the surface of the water. Scraping: Scraping against the bottom or sides of the tank. Flashing: Rapidly turning or flashing. Erratic Movements: Darting, whirling, or twisting movements. Loss of Equilibrium: Difficulty maintaining balance. Diagnosis Initial Steps in Diagnosis A comprehensive history of the disease should be supported by personal observations before conducting postmortem examinations. Routine Procedures Following Gross Appraisal Common diagnostic procedures include: Parasitological Examinations Bacteriology Histopathology The last two may require laboratory support. Diagnosis Initial Steps in Diagnosis A comprehensive history of the disease should be supported by personal observations before conducting postmortem examinations. Routine Procedures Following Gross Appraisal Common diagnostic procedures include: Parasitological Examinations Bacteriology Histopathology The last two may require laboratory support. Recommended Procedures for Investigating Disease Outbreaks (Anderson and Barney, 1991) On-Site Investigation: ✔ Examine fresh materials from healthy, moribund, and dead fish. ✔ Collect fish tissue samples for further analysis. ✔ Measure environmental conditions (e.g., temperature, oxygen levels). ✔ Investigate physical factors and rearing conditions. ✔ Gather information on the time-course of mortalities. ✔ Deliver suitable samples with accompanying information to the diagnostic laboratory promptly. Recommended Procedures for Investigating Disease Outbreaks (Anderson and Barney, 1991) Laboratory Procedures: Presumptive Identification of Pathogens: Assess for viral, bacterial, fungal, or parasitic infections. Positive Identification and Confirmation: Confirm the presence of specific pathogens. Drug Sensitivity Testing: Evaluate sensitivity to treatments and effectiveness of drugs. Additional Analyses: Conduct histopathology, toxicology, and other evaluations as needed. Recommended Procedures for Investigating Disease Outbreaks (Anderson and Barney, 1991) Importance of Correct Diagnosis Essential for selecting appropriate management strategies to address the problem and determine the best possible treatment. Provides a reference for developing future disease-preventive aquaculture procedures and practices. Final Diagnosis Recommendations Due to the need for specialized laboratory facilities and trained personnel, the final diagnosis of fish disease should be performed in accredited Fish Health Laboratories. Surveillance and Monitoring Initiating Disease Diagnosis at the Farm Level Hatchery or farm personnel can start disease diagnosis through regular monitoring of: Cultured populations Feed Environmental inputs Importance of Familiarity with Normal Conditions Understanding the normal health status of fish is crucial for spotting changes or abnormalities. Maintaining an adequate record of normal health conditions allows for effective assessment of deviations. Surveillance and Monitoring Role of Record Keeping Consistent record keeping is vital for monitoring the health status of cultured populations. Records help personnel identify environmental problems, learn from past mistakes, and minimize production costs. Surveillance and Monitoring Monitoring Frequency and Procedures The need for regular monitoring is directly related to the intensification of the production system: Extensive Systems: Minimal monitoring may suffice due to lower inputs. Hatchery and Intensive Systems: Regular monitoring procedures are essential. Examples of monitoring procedures include: Periodic microscopic evaluation of gill tissues for microbial fouling. Daily microscopic examination of larvae in culture tanks. Evaluation of culture tank water quality, algae, and other feed inputs. Surveillance and Monitoring Data Collection During Disease Outbreaks Gathering data on the following can provide valuable insights during a disease outbreak: Patterns of losses Species and sizes of affected fish Duration of the epizootic Indicators of Environmental Problems vs. Infectious Diseases Acute Environmental Problems: Sudden, explosive die-off of all fish typically indicates issues like: Lack of oxygen Presence of lethal chemical toxicants Lethal temperature extremes Infectious Diseases: Mortality may start with a few sick fish showing: Unusual behavior Loss of appetite Infectious diseases can vary in duration and severity, with mortality rates ranging from high daily losses to low percentages over several weeks. Indicators of Environmental Problems vs. Infectious Diseases ▪ (A) acute environmental failure ▪ (B) acute infectious disease ▪ (C) chronic infectious disease